At the present time there are at least three types of shade systems designed for use in greenhouse-type solar rooms. One system uses folded shades with each fold connected at one point to tracks along the sides. These shades are not efficient insulators because the side edges of each fold are not sealed throughout their length to the tracks. Furthermore, the folds frequently become unsightly due to the lack of uniformity of the folding action, particularly when the shades are retracted.
Another system employs tracks that are build into the glazing bars that separate the adjacent vertical glass bays. Because the tracks are built into the glazing bars, the system is not suitable for retrofitting into existing structures but rather must be included in the structures when initially built. Similarly, the system employs spring motors which are built into the sills. Thus, both the sills and glazing bars are fairly complex structures and are rather large, which results in increased costs to the purchaser. The purchaser of a structure which incorporates this system has to pay for the special glazing bars and sills whether or not he wants the insulating shade system. Another disadvantage of this system is that the shade material is required to enter the tracks which are incorporated into the glazing bars at an acute angle, which interferes with the smooth operation of the system.
Yet another system found in the prior art employs large, heavy metal tracks which are secured to the glazing bars. The metal tracks must be factory bent to the exact curve of the greenhouse glazing bars, as they are not capable of being bent at the site. Consequently, the tracks must be manufactured to rather precise specifications, which has an adverse effect upon their cost. This system also employs large weights for drawing the shades down the tracks, and these weights are quite unsightly, as they are normally suspended in the middle of the greenhouse bays.
Heretofore, the use of plastics in the manufacture of tracks has been avoided, as people in the industry believed that regardless of the plastic composition, the tracks would deform under the heating and cooling cycles to which they are subjected, particularly when the tracks were mounted in long sections of 20 feet or more, Furthermore, it has been generally assumed that plastic materials could not withstand the high temperatures and ultraviolet exposure, present in the high temperatures and ultraviolet exposure, present in sunroom areas.
Many conventional shading systems for sun rooms, particularly the second system described hereinabove, employ a spring device, such as a spring motor, to retract the shade material over the glazing surfaces. These spring motors generally use a conventional zero gradiant or constant force spring. Such constant force springs exert on the partially retracted shade material a generally constant pull force and a torque which increases at a relatively constant rate over a narrow range as the cable is extended. However, the pull force actually required to retract the shade is not constant but varies depending upon the position of the shade in the tracks, or, upon the length of cable withdrawn. For most such systems, the pull force required to retract the shade increases slowly until about half of the cable is withdrawn. Thereafter, at some point, depending upon the particular shade configuration, the amount of pull force required to retract the shade decreases substantially, Since the constant force spring must be designed to provide a pull force which at all times is greater than the maximum force required to retract the shade, a large disparity exists between the pull force actually required to retract the shade and the actual pull force exerted. As a result, an unnecessary strain is placed upon the shade material and upon other components of the system. Typically, these constant force springs are produced by deflecting the spring material to an equal degree along the entire length of the spring so that each section has an essentially constant coil diameter.
The principal object of the present invention is to provide a retrofittable system that can be easily measured and installed in the field, that is easy to ship, that works well, and that is not too costly.
Another object of the present invention is to provide a retrofittable insulating shade system for greenhouse-type rooms, which operates smoothly, and which makes use of sealed, tracked, insulating window shades which will render such rooms substantially immune from the extreme cold of winter and the extreme heat of summer, and provide privacy when desired, so as to enhance the enjoyment provided by such greenhouse-type sun rooms.
A further object of the present invention is to provide a spring motor for a retrofittable insulating shade system in which the profile of the curve of the actual pull force exerted on the shade material at each position of the shade conforms to the profile of the curve of the pull force actually required to retract the shade.